The present invention is directed to air filters and more specifically to continuously operating air filters which are utilized to filter the particulate impurities from extremely contaminated air streams, and which are so constructed as to be continuously cleaned.
Most modern industrial environments require conditioning of the air space therein from the standpoint of several characteristics. Temperature must be controlled; humidity must be controlled; and the percentage of contaminants in the air must be controlled. Various reasons exist behind these conditioning requirements. Often the manufacturing or industrial operations being carried on in the work place dictate a certain temperature, humidity, or maximum level of contaminants in the air. Health and safety regulations now required that the environment in which workers perform their tasks must be free of unhealthy contaminants.
One specific example of an industrial application in which recent health and safety standards have required a reduction in the level of airborne particulates is in the processing of cotton. For decades cotton mills in which raw cotton is opened, combed, carded, and spun into yarn have been one of the most contaminated, unhealthy environments in which an industrial worker could possibly exist. Numerous cases of brown lung trace their causes to the cotton mill. Other industrial environments are similarly required to be cleaned in accordance with contemporary health and safety standards.
Some environments, such as the cotton mill, create such a contaminant laden atmosphere that continuous filtering of the air is required. It is not satisfactory to filter the return air most of the time, then to shut the system down periodically for cleaning or replacement of filters. The filtering operation must be continuous. Further, any filter media utilized in such environments loads so quickly that cleaning of the filter must be substantially continuous also. It is this type of environment with which the present invention is directed.
Continuously cleaned filters of the type in which a filter or filters are continuously cleaned by some type of movable nozzle or air plenum are known and illustrated to some extent by U.S. Pat. No. 3,951,627 to Barr, Jr. et al. Such systems are relatively expensive and the system shown by Barr utilizes a system of filter bags which are periodically cleaned by backwash air, rather than a screen.
The U.S. Pat. No. 4,372,713 to Kean, Jr. is another example of the utilization of backwash air to clean bag-type filter apparatuses. The U.S. Pat. Nos. 1,493,110 to Deihl and 1,729,527 to Titgen are examples of systems in which two, substantially duplicate filter systems are alternatively used, one providing a cleaning function while the other is being cleaned. In such systems, the air paths and filter functions are generally separated and duplicated. Thus, such types of systems are relatively expensive.
In the present invention, however, a unitary housing and single, surface loading screen-type filter element are utilized in conjunction with a pair of movable vanes which alternately direct the air to one side section of the screen, then the other. As the dirty air is directed to one side of the screen the opposite side section thereof is isolated therefrom and provided with a backwash of air pulled through the opposite side of the screen to remove the impurities there collected. The backwash air, after serving its impurity flushing function, recirculates beneath the vanes and flows out through the system in a forward direction with the clean air.
Looking more closely at the invention there is provided a method and apparatus for continuously separating particulate impurities, such as cotton dust and small fibers, from an air stream while cleaning the separating media. For this purpose there is provided a filter housing having an air permeable filter screen intermediate the front and rear wall thereof forming a front intake chamber and a rear discharge chamber. A pair of air impermeable vanes pivotally mounted on opposite sides of a dirty air inlet in the front wall of the housing are swingable or movable between a first position where the vanes form a first conduit directing the dirty air toward the left-hand side of the filter member, and a second position where the vanes form a second conduit directing the dirty air toward the right-hand side of the filter member.
With the vanes in the first position backwash air is introduced through an inlet in the upper portion of the right-hand side of the rear wall, through the right-hand portion of the screen, beneath the vanes, and back out through the left-hand portion of the screen. The vanes are then switched to the second position so that the right-hand side of the filter screen serves to clean the dirty air, while the left-hand side is flushed clean of the impurities collected thereon.
A backwash air inlet is provided in confronting relationship with each side of the filter screen in the upper portion of the rear wall while discharge outlets corresponding to each side of the filter screen are provided in the lower portion of the rear wall. Dampers associated with each inlet and outlet operate in timed relation with the movement of the vanes to open the appropriate backwash air inlet at a prescribed time while the other remains closed and to control the opening of the clear air discharge outlets at the prescribed time in relation to vane movement.
A particle collection receptacle is positioned below the intake chamber to receive contaminants flushed therefrom by the backwash air flow path. Control motors are connected to the vanes, backwash dampers, and discharge outlet dampers and are so electrically controlled that upon movement of the vanes to one side of the filter screen, and in a prescribed time sequence, the appropriate outlet and backwash damper open while the other outlet damper and backwash damper close.
It is therefore an object of the present invention to provide an improved and simplified filter apparatus and method for continuous, uninterrupted operation in the cleaning of extremely dirty air paths.
It is another object of the invention to provide a filter method and apparatus of the type described in which the incoming dirty air is first directed toward one section of a screen while the opposite section is cleaned, then directed toward the opposite side of the screen while the first side section is cleaned.
It is yet another object of the present invention to provide a method and apparatus of the type described in which the filter operation is carried on in a single enclosure.